Adjustable magnetic apparatus



May 9, 1939- P. D. CROUT 2,157,324

ADJUSTABLE MAGNETIC APPARATUS Filed Oct. 26, 1954 2 Sheets-Sheet l FIG.I

INVENTOR PRESCOTT D. CROUT ATTORNEY May 9, 1939. P. D. GROUT 2,157,324

ADJUSTABLE MAGNETIC APPARATUS PRESCOTT D. BY Mm ATTORNEY Patented May.9, 1939 UNITED STATES PATENT OFFICE ADJUSTABLE MAGNETIC APPARATUSPrescott D. Crout, Boston, Mass., assignor to Raytheon ManufacturingCompany, Newton, Mass, a corporation of Delaware Application ctober 26,1934, Serial No. 150,117 '7 Claims. (01. 111-119) This invention relatesto an adjustable magnetic apparatus, and more particularly to such anapparatus in which the inductance thereof may be varied.

An object of this invention is to provide such an apparatus in which thecurrent through said inductance is varied directly in accordance withthe magnitude of motion of a controlling member. Another object of, theinventionis to devise a novel supporting structure for the movablemagnetic member of such an apparatus. I

,' A still further object is to .provide a device of the kind indicated,which is simple and sturdy Fig. 2 is a top view of the apparatus shownin Fig. l with certain portions broken away;

I Fig. 3 is a cross-section of the upper portion of the structure takenalong line 3-3 of Fig. 2; and

of the movable magnetic bar.

In my co-pending application, Serial No.

a 742,913, I have described and claimed a combined transformer andinductance control unit which is to be used in a welding machine. Thepresent apparatus constitutes an improved form of the combinedtransformer and inductance control unit shown in said co-pending'application.

In any adjustable magnetic apparatus in which the inductance is variedby varying an air gap, it is difficult to obtain a linear change of 4susceptance in accordance withthe magnitude of movement of thecontrolling member of the system. This is probably due to the fact thatproduce comparatively large changes in the susceptance, while with alonger air gap, a smaller" change in the length thereof will produce amuch smaller change in susceptance. In my present invention I haveeliminated this difficulty by moving a magnetic bar so as to produce avariable air gap by means of a controlling member in such a way as toproduce a relatively small change in the air gapjper unit distance ofmotion ofsaid controlling member when said air gap is small, andan'increasingly'sr'eater' change in the air gap per unit distance ofmotion of said controlling member as the length of the airgap increases.I I I Fig. 4 is a side view of one of the laminations In thedrawings thecombined transformer and inductance control unit consists of atransformer l and a variable inductance 2. The various coils of thetransformer i and the inductance 2 are preferably mounted on a combinedcore member 3 having three legs 4, 5 and 6 upon which the transformercoils are wound, and three additional legs 1, 8 and 9 upon which thethree inductance I coils i0, II and i2, respectively, are wound. Thecombined core member 3 has yokes l3 and ll completing the magnetic pathfor the transformer, the yoke l4 forming.

also part of the magnetic path for the inductance coils Ill, ll and I2.I, 8 and Bare formed with substantially flat pole faces and a movablemagnetic bar I5 is disposed adjacent the outer ends of said pole faces.The

magnetic core 3 and its associated coils are mounted within a frame it.This frame--'-has formed thereon a number: of arms I'i; whereby theentire unit may be bolted in place into such The upper ends of the legsa welding machine as shown in my co-pending application referred toabove. The said core may be bolted in place on said frame it by means ofa plurality of bolts 18. The coils III, II and I2 are easily assembledon the legs I, 8 and 3 by being slipped over-the outer ends of theselegs, and are retained in place by a plate i9 which may be formedof somesuitable material, such as an insulating board. I The plate I9 isretained in place on the legs], 8 and 9 by means of bars clamped onopposite sides .of each leg I, 8 and 3 by means of bolts 2i.

Although I have described the above ratus as consisting of both s.transformer and an inductance unit, this invention is concernedprimarily with the inductance unit itself. Thus this inductance unitcould be an entirely separate member having a diflerent number .of legsand pole faces than thatidescribed above, and likewise such inductanceelement may be useful in a cast number of instances aside from use'in anarc welding machine. I

In order that the inductance of the element 2 be variable, the magneticbar I! is movable with respect to the pole faces of the legs 1,3 and 9in such a manner as to produce a variable air gap adjacent each of saidpole faces. In order to support said magnetic bar i 5, a frame 22- isbolted to the frame l6 at the upper end thereof by means of a pluralityof bolts 23. The frame 22 is provided with four cams 24, which cams formthe supporting and guidingmembers for the magnetic bar it. The magneticbar l5 itself consists of a plurality of magnetic laminations '26mounted within a sub-frame 25. One of these laminations 26 is shown inFig. 4. As will be seen, the lamination is entirely imperforate and isprovided with two projecting ears 21. In order to assemble thelaminations within the subappa-,

frame 25, these laminations are merely Slipped into said frame 25 withthe ears 2'! resting on the two ends of said sub-frame. In order thatthese laminations be tightly packed, a wedge 26 which may be made ofsome suitable material, such as brass, may be inserted between the sideof subframe 25 and the laminations 26. Since the subframe 25 consistsmerely of a hollow rectangular member, the sides thereof possessconsiderable flexibility. In order that the laminations be still morefirmly clamped within said sub-frame, said sub-frame is provided withupstanding ears 29 through which passes a bolt 30. By clamping the bolt30 onto said ears 29,-the sides of the sub-frame 25 may be bowed insumciently to insure a firm clamping action on the sides of thelaminations 26. It will beseen that these laminations are not providedwith perforations for the-purpose of v bolting them into place on thesub frame. This results in an extremely simple form of lamination whichis easily constructed and easily assembled. Due to the fact that themajor force exerted on the laminations tends to move them in toward thepole faces of the legs I, 8 and 9' and since the ears 21 on thelaminations 26 oppose such motion, the resultant action one whichretains the laminations firmly in place in the desired position withrespect to the sub-frame 25.

In'order to support the magnetic bar I5 on the cams 24, the sub-frame 25has formed integrally therewith the four sleeves 33 at the four cornersthereof. Two shafts 34 are passed through the two end pairs of sleeves33, and are retained in placetherein and prevented from turning by somesuitable means, such as pins 35. The shafts 34 project beyond the outerends hooked over projections 38 formed at the two and undesirablevibration of'themagnetic bar' I5 with respect to the rest of thestructure. This action is more fully described and claimed in my saidcopending application. In order that this function shall occur, thetension springs 31 are designed to exert sufiicient pull on the magneticbar I5 so that no chattering occurs between-the bar I5 and itsassociated structure.

It is difficult to support a rigid bar'" at four movable points inasmuchas each of said points should be in intimate contact with its respectivesupporting surface so that excessive backlash and play is avoided andthus undesirable vibration and impact eliminated. In my device thisdifllculty has been avoided, and the four rollers 36 are'alwaysmaintained in intimate contact I with the four cams 24. Due to the factthat the sub-frame 25 is a simple rectangular member and the laminations26 are merely inserted into said sub-frame, theresultant structure has aconsiderable amount of torsional flexibility. Thus even if the cams 24are not accurately aligned, the sub-frame 25 will, under the actionline.

of springs 3'I,twist so that each roller 36 is In intimate contact withits respective cam 24. The absence of any fastening member passingthrough the laminations 26 permits them to slide by each other to somedegree, and thus the magnetic bar I5 participates accurately in thetwisting of the sub-frame 25. In constructing the device, nospecialprecautions'need be taken to align the cams 24 or the rollers 36accurately. When assembled the bar I5 will always be firmly supported at"the four corners. The flexibility of the bar I5 and sub-frame 25 offersno disadvantage since when it is seated upon the cam 24 the rigidity ofthe frame 22 gives to the entire assembly the requisite stiffness.

In order further that the rollers 36 bear equally on the four cams 24,it is desirable for the force pulling the bar |5 toward the pole facesof the legs I, 8 and 9 to act through the center of said bar. Thus theprojections 38 are located on the center line of bar I5, and the springs31 exert their force along's'aid center The magnetic forceacting' on themovable magnetic bar I5 also'ls exerted in such a way that the resultantforce may be considered'as acting through the center of said magneticbar. It is ordinarily very diflic'ult to dispose the movable magneticbar so that this result is obtained. In my device I have eliminated thisdifliculty by arranging the laminations 26 so that the central line 3|of'the magnetic bar I5 is at all times nearer the pole faces of the legsI, 8 and 9 than the rest of said magnetic bar on either side of saidcentral line. This is accomplished by shaping the two ends of thesub-frame 25 so that the upper sides 32 thereof are shaped as indicateda by the dotted line .in Fig. 3. Thus merely by inserting identicallaminations 26 into the subframe 25, the resultant magnetic bar takesthe shape as shown in Fig. 3. Since the center of the magnetic bar I5 isthus disposed so that it is nearest to thepole faces of the legs I, 8and 9, the resultant magnetic force exerted on said magnetic bar isaccurately centered on said bar.

In order to produce the desired adjustment and motion of the bar I5, asuitable controlling arrangement is .provided therefor. Rotatably'mounted on the bolt 30 is one end of a link 40.

The other end of said link is rotatably connected to one end ofa rod 4|.The rod 4| is free to slide through a sleeve 42 carried by a cross-bar43 'mountedon the upper side of the frame 22. Although the rod 4| isfree to slide in said sleeve 42, it cannot turn therein. This is due tothe fact that the link 40 connected to the end of rod 4| .cannot turn,and thus prevents rod 4| from turning. The opposite endof the rod 4|projects through said sleeve 42, and is threaded through asu'bstantiallength as indicated at 44. An actuating member -45 is provided withinternal threads which engage the, external threads 44 on the rod 4|.The outer end of the threaded portion 44 ofthe rod is provided with astop member 46 whichis fastenedin place on said rod 4| after the member45 has been threaded,

into place. In addition to the springs 31, asmall biasing spring 41 15provided which tends to move the reactor bar I5 to the left, as shown inFig. 1, and likewise tends to move the link 40 and rod 4| in this samedirection. Due to this biasing action, the actuating member 45 is biasedso that it firmly engages the outer end of the sleeve 42. .In order torotate the actuating member 45, itis provided-with a sprocket 46 whichis engaged by a chain 49. Any suitable mechanism for moving the chain 48may be used.

Preferably the actuating mechanism may consist of the arrangement asshown in my said co-pending application. It will be seen that as theadlusting member 45 is rotated, the rod; 4i will-be moved to the left orright as shown in Fig. 1. As

. the rod 4i moves to the right, the magnetic bar ll as pointed outabove. This action causes the air gap at the outer ends of the 'polefaces on legs 1, 8 and 9 to decrease, and thus increases the inductanceof the coils ll, Ii and I2. As the rod 4i moves to the left, andmagnetic bar I! likewise is moved to the left, the rollers 36 are causedto ride up on the cams 24, thus increasing the air gap and decreasingthe inductance of the coils Ni, ii and i2.

As will be seen from Fig. 1, the cams 24 are so formed that as the rod4| moves to the left a definite distance when the magnetic bar i5 is inits lower position, a relatively small change in the relative positionbetween the magnetic bar and its associated pole faces occurs. Thus arelatively small change in the length of the air gap is produced. Towardthe upperposition of the bar l5, however, if the rod 4! is moved to theleft the same distance, a much greater change in the air gap isproduced. Although the cams 24 can be designed so that the inductance ofthe coils Ill, ii and i2 varies in any desired relationship with respectto the movement of the actuating member 45, I prefer that these cams beformed in such a way that the susceptance of said coils changessubstantially linearly with the angular distance through which theactuating member 45 is moved. Thus when the device is used in such anarc welding machine as described in my copending application, thecurrent through the load will vary substantially linearly with theangular distance through which said actuating member is moved. I findthat these conditions may be satisfied by circular cam surfaces.

It is to be understood that this invention is not limited to theparticular details of the arrangement as described above'as manyequivalents will suggest themselves to those skilled inthe art. Forexample, certain aspects of my invention may be' useful in any magneticapparatus in which an adjustable air gap is-desired, even those in whichbut a single such air gap is provided. Various other changes and uses inand for the various novel parts of my invention will readily suggestthemselves. It is accordingly desired that .the appended claims be givena broad interpretation commensurate with the scope of the inventionwithin the art.

What is claimed is:

1. In a magnetic apparatus, a magnetic core, I

'said supporting surfaces, whereby said bar is always maintained firmlyseated against said supporting surfaces.

2. In a magnetic apparatus, a magnetic core, means for setting up amagnetic flux in saidcore, said magnetic core having a variable air gapbetween a pole face and a movable magnetic bar, said movable magneticbar comprising a hollow frame member and a number of laminations ofmagnetic material inserted in said frame member,-and abutments on saidlaminations engaging surfaces on said frame member and opposing motionof said laminations under action of said magnetic flux, whereby saidlaminations are retained in place in said frame member.

3. A magnetic bar comprising a hollow frame member and a number oflaminations of magnetic material inserted in said frame member, andabutments on said laminations engaging surfaces on said frame member andopposing motion of said laminations under action of a magnetic flux,said frame member having side members and end members, said side membershaving sufficient flexibility to permit said laminations to be yieldablywedged into said frame member.

4. A magnetic bar comprising a hollow frame member and a number oflaminations of magnetic material inserted in said frame member,abutments on said laminations engaging surfaces on said frame member andopposing motion of said laminations under action of a magnetic flux,said frame member having side members and 'end members, said sidemembers having suflicient flexibility to permit said laminations to beyieldably wedged into said frame member, and means for clamping saidside members against the sides of said laminations.

5. In a magnetic apparatus, a magnetic core, means for setting up amagnetic flux in said core, said magnetic core having a variable air gapbetween a pole face and a movable magnetic bar, the face of saidmagnetic bar facing said pole faces being disposed in more than oneplane, the center line of said face being disposed closer to said polefaces than the rest of said face, whereby the center of the magneticforce exerted by said magnetic flux is centered on said magnetic bar.

6. In amagnetic apparatus," a magnetic core, means for setting up amagneticfiux in said core, said magnetic core having a variable air gapbetween a pole face and a movable magnetic bar, the face of saidmagnetic bar facing said pole faces being disposed in more than oneplane, a

predetermined portion of said face being disposed closer to said polefaces .than the rest of said face, whereby the magnetic force exerted bysaid magnetic flux is centered on said predetermined portion.

'7. In a magnetic apparatus, a magnetic core, means for setting up amagnetic flux in said core, said magnetic core having a variable air gapbetween a pole face and movable magnetic bar, means for supporting saidmagnetic bar at a plurality of movable points on opposite sides of thecenter line of said magnetic bar, the'face of said magnetic bar facingsaid pole faces being disposed in more than one plane, the center lineof said face being disposed closer to said pole faces than the rest ofsaid face, whereby the center of the magnetic force exerted by saidmagnetic flux is centered on said magnetic bar, and the said force issubstantially equally divided between the 1siupporting points onopposite sides of said center PRESCOTT D. GROUT.

